Because Destiny isn’t a Battle Royale. It is more like MMOs like Black Desert and Elder Scrolls Online. Games that have some form of monthly subscription fees in order to cover the cost of new content. If you just wish to play the pvp part of the game, there is a part of the season pass that is free, and pvp itself is free. But the only game that has free pve content like Destiny is Warframe. However this comes at the cost of an extremely aggressive and constantly in-your-face microspending system. One that shamelessly lets you buy your way around a needlessly grindy base game.